This research extends prior work on hospitals that treat a large proportion of black patients to cancer care and on racial variation in the treatment of prostate cancer. Nearly half of black men with prostate cancer tend to receive care from hospitals with a high proportion of black patients. In contrast, a relatively small proportion of white patients receive care from these same hospitals. There exist significant differences in the rates of definitive therapy between hospitals; hospitals with high proportions of black patients had significantly lower rates of definitive treatment, and this association did not differ by patient race. Among patients who were treated, there did not appear to be differences between rates of prostatectomy versus radiation by hospital racial composition.
Why might hospital racial composition be associated with treatment decisions? The first hospital assignment may indicate the point of entry into care, and the most frequent hospital represents the hospital where men tend to receive care. In both cases, hospital assignments are meant to reflect the different institutional environments in which care is received. The hospital assignments may denote the ways in which the health care delivery system—including hospitals and outpatient care—is clustered within a particular area.27
The clustering of care may lead to distinct physician practice styles,13
for example through the diffusion of innovation.25,32,33
Variation in practice styles may be especially prevalent in the setting of prostate cancer’s clinical uncertainty.11,34
In addition to reflecting distinct practice styles, hospital racial composition may indicate different levels of access to care. Significant differences have been identified among primary care physicians who tend to serve white and black patients,18
with physicians who treat black patients reporting greater difficulty accessing high-quality specialty care. In our sample, hospitals that served high proportions of black patients also had higher rates of Medicaid admissions. Rates of Medicaid admissions, which tend to have lower reimbursements, along with rates of unpaid or charity care may affect health system finances, potentially causing negative spillover effects for Medicare beneficiaries. We found some evidence of this spillover effect with higher percentages of Medicaid admissions associated with lower rates of definitive treatment for the Medicare beneficiaries in our sample. We were, however, unable to adjust for hospital rates of unpaid or charity care.
Although access to specialty care in certain hospital systems and geographic locations may be limited, different hospital assignments likely reflect differing choices about where to seek care. It is possible that patients’ preferences regarding choice of hospital and specialist may covary with their choice of treatment; for example, distrust in the medical system may underlie both decisions.35
However, evidence suggests that patients rely heavily on their primary care physicians when deciding where to receive surgical36,37
and cancer care.36,38
Physician decisions regarding referrals to specific cancer providers remain poorly understood,39
and it is uncertain the extent to which providers currently take into account how referral patterns may alter the eventual care their patients receive.
More broadly, hospital racial composition may be a marker for patient-level and neighborhood-level socioeconomic status and for residential racial segregation.40,41
In accordance with the results of prior studies,2,16
income (at the neighborhood level) was independently associated with higher rates of definitive treatment. Hospital racial composition has been linked to residential racial segregation,40
and residential segregation has been linked with differences in rates of prostate cancer treatment and higher rates of mortality among black men with prostate cancer (K. Armstrong et al, unpublished data). It is plausible that hospital racial composition may, in part, mediate treatment differences because of residential racial segregation.
Considering that lower rates of treatment for black men persisted after accounting for hospital racial composition, additional explanations are required to understand these differences. It is possible that patient knowledge, preferences, and decision-making styles with regard to prostate cancer may vary between white and black patients.42
Moreover, these beliefs may change over time, helping to account for changing patterns of treatment observed in our data. Decision aids may improve patient knowledge regarding prostate cancer treatment, although their impact on treatment choice and racial differences in treatment require additional investigation.43
Another plausible explanation for the various rates of treatment for black patients may be that physicians working within the same hospitals may help patients reach different treatment decisions. Supporting this, Denberg and colleagues used clinical vignettes to demonstrate that urologists made different recommendations regarding prostate cancer treatment for patients of different races and social vulnerability.44
Additional variation may stem from black men being less likely than white men to have a consultation with a radiation oncologist before treatment.45
Specialists are more likely to recommend their own treatment modality,46,47
and men who were not seen by a radiation oncologist are less likely to receive radiation therapy.45
The observed clustering of patients according to race has important implications in the setting of health care reform. Recent reforms have focused on the relationships between outpatient physicians and hospitals, for example attempting to create accountable care organizations. In these arrangements, it is hoped that hospital-led care delivery and payment may lead to improved coordination and cost reductions.48,49
The creation of accountable care organizations may reify existing differences in where white and black patients tend to receive care and exacerbate observed racial differences in treatment patterns.50
There are multiple limitations to the study. First, lower rates of treatment in patients with low risk of disease would not necessarily represent lower quality of care.11
Second, patients were assigned to hospitals where they were likely to be evaluated or received care for their cancer. Because it was not always possible to definitively assign patients, multiple different methods were used, showing consistent results. Hospital matching was higher for white versus black patients, which may also affect our results. Third, we were unable to determine whether physician-level characteristics may mediate the observed relationships. Fourth, hospital volume measures were defined using Medicare beneficiaries, which miss younger patients who are more likely to undergo active treatment for prostate cancer. Prior studies have shown that urologist volume as calculated from Medicare data is highly correlated with total patient volume.51
Fifth, because of the availability of data, hospital racial composition is determined using data starting in 2002, although it is unlikely that hospital racial composition would have significantly changed over the study period. Sixth, our models of first hospital assignments did not converge when adjusting for additional hospital-level features. Results based on logistic regression models (not adjusting for hospital clustering) were similar to the most frequent hospital assignment findings. Lastly, an area-level measure of income was used as a proxy for individual socioeconomic status.
In the setting of clinical uncertainty, where treatment for localized prostate cancer remains controversial, differences in treatment based solely on patient race warrant careful examination. Institutional factors as measured by hospital racial composition are associated with the care that both black and white patients receive, and interventions that focus solely on patient-level factors are unlikely to eliminate differences in care. Black men are much more likely to receive care at a certain subset of hospitals, and patients seen at these hospitals are less likely to undergo definitive treatment. Research and policy should focus on not only how patients come to receive care at specific hospitals but also why these environments are associated with various types of care. Understanding both steps is crucial when designing interventions to reduce differences in care.